Fig. 9
From: Determining polar ionospheric electrojet currents from Swarm satellite constellation magnetic data
Corresponding to Fig. 2 for Swarm Alpha, orbit 6493 on 20.01.2015 12:37 to 13:02 UT, including induced currents. The top panel shows observations, \(\delta F\), in green along with the model predictions, \(\delta F^{{\mathrm{mod}}}\), for three solution methods, \(L_1\) norm (black), \(L_2\) norm (red), and \(L_2\) norm without Huber-weighted misfit (blue). The middle panel shows the model residuals, \(\Delta \delta F\), for the same inversion methods, and the bottom panel shows the corresponding sheet current densities, J, again for all three methods. The sheet current densities are found using \(\alpha ^2 = 6.5\cdot 10^{-15} \frac{\text {nT}^2}{\text {A}}\) for the \(L_1\) norm solution and \(\alpha ^2 = 1\cdot 10^{-26} \frac{\text {nT}^2}{\text {A}^2}\) for the \(L_2\) norm solutions. A positive current flows from midnight to noon (sunward)